In the current illuminating devices in common use, the LED illuminating devices are widely used due to their performances of energy saving and high efficiency to replace the illuminating devices such as filament lamps or fluorescent lamps. For example, as the LED technology is widely used, the light source of most of the T8 luminaires is changed to the LED light source using the LED technology, and the suitable LED driver is correspondingly used, such that the fluorescent light source is removed while the tube sockets of the T8 lamp are retained in the respective luminaire. In this way, the manufactured light source has the appearance of the T8 lamp, while it is equipped internally with the light source having the LED performances. In the above improvement on the T8 lamp, the ECG electronic ballast for driving the fluorescent lamp may not be removed from the luminaire because the latter one remains installed, and thus furthermore the ECG type keeps hidden, but some ECGs dedicated to the fluorescent light source often are not applicable to the LED light source because of the problem that the LED light source usually may not be compatible with different ECG types.